Control system



Aug. 4, 1:531. H, E, TRENT 1,315,942

' CONTROL SYSTEM V Filed March 14, 1925 f I 2% 5 7 0 im L- g INVENTOR Harold Tltflf ATTORN EY Patented Aug. 4, 1931 PATENT OFFICE HAROLD E. TRENT, OF LANSDOWNE, PENNSYLVANIA ooNrBoL sysrnivr Application filed March 14, 1925. Serial No. 15,561.

. My invention relates to control systems and particularly to protective means forde- Vices in such systems.

One object of my invention is to provide a control system for an electric circuit that shall have a resistor which shall be controlled only by a responsive relay of the system and the main switch in the circuit for limiting the current in the actuating winding of the main switch and in the responsive relay.

Another object of my invention is to provide a system of the above indicated character in which the limiting effects of the resistor are varied depending upon the operation of the main switchand the relay.

Another object of my invention is to pro- I such as a heater winding, a motor windlng vide means for protecting a thermostat and the winding of an ordinary double-break switch without the use of auxiliary contact members on the switch.

Another object of my invention is to provide a single resistor that shall serve the double purpose of protecting the contacts of a thermostat and the windingof a standard electrically operated switch.

A further object of'my invention is to provide a system ofthe above indicated character that shall besimple and inexpensive to make and effective in its operation.

In practicing my invention as applied to an electric system of temperature control, I provide a standard double-break electromagnetically operated switch for controlling the circuit. A thermostat is provided for controlling the circuit of the winding of the switch and a resistor is so permanently connected between the winding, the thermostat and the bridging contact member of the switch that a portion of the resistor is connected in circuit with the winding when the thermostat is so actuated as to energize the winding to close the switch, and when the switch is closed allot the resist-or is connected 'in circuit with the winding and a portion is connected in circuit with the thermostat to protect the same should the seating of the contacts of the switch be defective.

With this arrangement the thermostat and the switch winding are protected from being burned out and the protection is efiected invention. 55

An electric circuit 1 comprises a load 2 or any electrical element to be controlled. The conductors 3 and 4 of the circuit are connected to the winding 2 and to a source of electromotive force (not shown). A switch 5 has two stationary contact members 6 and 7 which are in circuit with the conductor 4, a bridging contact member 8 and an electromagnet 9 for actuating the member'iS 8. The movable core member 10 of the electromagnet is'actuated by a winding 11.

A thermostat 12 comprises, in general, two stationary contact members 13 and 14, and a movable contact member 15 which is actuated 5:0 in accordance with the temperature of the device being controlled by the winding 2. While I have shown a thermostat, it is, of course, just as feasible to use a primary contacting device such as a pressuregauge, cur- 7 rent responsive relay, or manually operated switch or contact mechani m, depending upon what function it is desired to control the winding 2 in accordance with.

The contact member 1 10f the thermostat 1 12 is connected to the conductor 4 and the contact member 13 is connected to the conductor3 as is also the termin a1 16 of the winding 11. The other terminal 17 of the winding is connected to one terminal of a resistor 18. the other terminal of which is connected to the bridging contact member 8 of the switch.

lVith the arrangement specified in c0nneccircuit at the moment contact members 13 tion with Fig. 1 when the temperature falls to such value that the member 15 of the thermostat engages the contact member 141-, a circuit will be completed from the conductor t through the contact members 1i and 15, the mid-point tap 19 of the resistor 18, a portion of the resistor, and the winding 11 to the other conductor 3. This energizes the wind ing 11 from the circuit 1 and causes the bridging member 8 to engage the contact members 6 and 7 to complete the circuit of the winding 2. T he amount of current through the contacts 14 and 15 is limited by a portion of the resistor 18.

lVhcn the switch 5 is closed a circuit is completed from the conductor 4: through the bridging member 8, all of the resistor 18 and the winding 11 to the conductor 8. Thus, when the temperature has changed to such value that the contact member 15 disengages the contact member 1-1 the winding 11 will continue to be energized with lower value of current as now all of resistance 18 is traversed thereby, such lower value of current being, however, effective to hold member 8 in bridging relation with contact members 6 and 7. Furthermore, should the bridging member 8 only be in engagement with one stationary contact member 6 a portion of the resistor 18 is always in circuit with the contact member 15 to preclude causing the contact members let and 15 from carrying an excessive current when in engagement, and drawing an are when they are disengaged.

hen the winding 2 has operated for a sufficient time to so increase the temperature that the member 15 engages the member 13 then the winding 11 and a portion of the resistor 18 are short-circuited to thus permit opening the switch 5.

Vith this arrangement it is unnecessary to provide extra contact members on the switch for switching in the current limiting resistor and at the same time this resistor serves to protect the contact members of the thermostat or other regulating relay.

In F 2 instead of using a single resistor I provide two resistors 20 and 21, the resistor 20 of which is connected between the terminal 17 of the winding 11 and the bridging member as before. The contact member 15 is also connected to the terminal 17 of the winding 11 and the resistor 21 is connected between the contact member 14 and the conductor 4.

lVith the arrangement shown in Fig. 2 the resistor 21 limits the current through the contact members ll and 15 under all conditions and the resistor 20 merely reduces the current through the winding 11 when the switch 5 is closed to preclude overheating, and as a means for limiting the current where the coil 11 is short-circuited for opening the main and 15 are in engagement.

In Fig. 3 the resistors 20 and 21 are connected as shown in Fig. 2, but they are disposed on a single spool for convenience of manufacturing. The operation is the same as set forth with respect to the arrzmgement shown in Fig. 2.

From the foregoing it will be seen that in the present improved control system the contact members 14; and 15 constitute switch means operable when closed to effect excitation of the closing coil 11 of switch 5 through part of the resistance means associated with the system, such as the resistor 18 in Fig. 1 and the resistors 20 and 21 in Figs. 2 and 3, such part being the resistor 21 in Figs. 2 and 3 and in Fig. 1 that part of resistor 18 to the left of tap 19. Further, the connections are such as to provide a holding circuit for the switch means 5 when the same in circuitclosing position, such connections, or such holding circuit, including another part of the resistance means, namely, resistor 20 in F igs. 2 and 3 and in Fig. 1 that part of resistor 18 to the right of top 19, and also including aconnection between this part of the resistance means and the movable contact member 8.

lVhile I have shown preferred embodiments of my invention, many changes may be made therein without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim as my invention:

1. A control system for an electric circuit comprising a. double-break switch, awinding for effecting closure of the switch, a thermostat for controlling the circuit of the winding, a resistor and means for so connecting the resistor that a portion thereof is in circuit with the winding when the thermostat is operated and all of it is in circuit with the winding when the switch is closed.

2. A control system for an electric circuit comprising a double-break switch, a winding for effecting closure of the switch, means responsive to a characteristic of the circuit being controlled for controlling the circuit of the winding, and a resistor so connected to the switch that part of it is connected in series with the winding when the responsive means is actuated and all of it is connected in series with the winding when the switch is closed.

3. A control system comprising a main circuit, a double-break electrically actuated switch for the circuit, a primary contacting device connected to the circuit for controlling the operation of the switch, a resistor, and means for so connecting the resistor that a portion of it is in series with the winding of the switch when the primary contacting device etfects closure of the switch and all of it is in series with the winding when the switch is closed.

4. A control system for an electric circuit comprising a double-break switch, a winding for effecting closure of the switch, a primary contacting device for controlling the winding, and a resistor so connected to the winding, switch and primary contacting device that the closure of the primary contacting device connects a portion of the resistor in circuit with the winding and the closure of the switch connects all of the resistor in circuit with the winding.

5. A control system for an electric circuit comprising two stationary contact members, a bridging contact member for cooperating with the stationary contact members to control the circuit, an electromagnet winding for actuating the bridging contact member, a contact device having a movable contact member and two stationary contact members, a resistor connected between one terminal of the electromagnet winding and the bridging contact member and a mid-point of which is connected to the movable contact member of the contact device, one stationary contact member of the contact device being connected to one conductor of the circuit and the other stationary contact member being connected to the winding and to the other conductor of the circuit.

6. A control system for an electric circuit comprising a switch, an-electrical actuating means therefor, a resistance in series with said means in a path between a contact member of said switch and a point in said circuit, a second switch having a contact member connected to an intermediate point of said path and a second contact member, and a second resistance connected in series with said contact members in a path between said intermediate point and a point in said circuit between which and said first point there exists a difference of potential.

7. A control system for an electric circuit comprising a switch, an electrical actuating means therefor, a resistance in series with said means in a path between a contact member of said switch and a point in said circuit, a second switch having a contact member connected to an intermediate point of said path and a second contact member, and a second resistance connected between said second contact member and a point in said circuit between which and said first point there exists a difference of potential.

8. A control system for an electric circuit comprising a switch, an operating coil therefor, a second switch responsive to effects pro duced by current in said circuit, a resistance in series with said coil and second switch to limit the current in said coil when said second switch is closed, and a second resistance in series with said coil connected to a contact member of said first switch effectively in shunt to said first resistance to increase the current in said coil when said second switch is closed and to reduce the current in said coil when said second switch is open and said first switch closed.

9. In a control system of the character described, an electrical circuit, switch-means connected in said circuit and operable to open and close the same, a closing coil for said switch means, resistance means associated with said system, second switch means operable when closed to efiect excitation of said closing coil through part of said resistance means, and connections providing a holding circuit for said first-named switch means when the same is in circuit-closing position, said holding circuit including another part of said resistance means.

10. In a control system of the character described, an electrical circuit, switch-means connected in said circuit and having a movable contact member operable to open and close the same, a closing coil for said switch means, resistance means associated with said system, second switch means operable when closed to effect excitation of said closing coil through part of said resistance means, and connections providing a holding circuit for said first-named switch means when the same is in circuit-closing position, said holding circuit including another part of said resistance means and a connection between the latter and said movable contact member.

In testimony whereof, I have hereunto subscribed my name this 5th day of March, 1925.

HAROLD E. TRENT. 

